#include<iostream>
#include<string>
int main()
{
    std::string s="hello world";
    int all=s.size();
    std::cout<<"s删除前:"<<s<<std::endl;
    std::cout<<"all:"<<all<<std::endl;
    s.erase(0,all);
    std::cout<<"s删除后:"<<s<<std::endl;
    return 0;
}